Electronic device manufacturers strive to produce a rich interface for users. Conventional devices use visual and auditory cues to provide feedback to a user. In some interface devices, kinesthetic feedback (such as active and resistive force feedback) and/or tactile feedback (such as vibration, texture, and heat) is also provided to the user, more generally known collectively as “haptic feedback” or “haptic effects”. Haptic feedback can provide cues that enhance and simplify the user interface. Specifically, vibration effects, or vibrotactile haptic effects, may be useful in providing cues to users of electronic devices to alert the user to specific events, or provide realistic feedback to create greater sensory immersion within a simulated or virtual environment.
In order to generate vibration effects, many devices utilize some type of actuator. Known actuators used for this purpose include an electromagnetic actuator such as an Eccentric Rotating Mass (“ERM”) in which an eccentric mass is moved by a motor, a Linear Resonant Actuator (“LRA”) in which a mass attached to a spring is driven back and forth, or a “smart material” such as piezoelectric, electro-active polymers or shape memory alloys. Many of these actuators, and the devices that they interact with, have built-in resonant frequencies that optimally are dynamically determined and controlled so that drive signals that generate the haptic effects can be most effective and efficient, such as the optimization of an LRA device as disclosed in U.S. Pat. No. 7,843,277.
The performance characteristics of an actuator such as the rise time, brake time, and steady state voltage, may vary based on the design and manufacturer of the actuator, and may also change during the life of the actuator because of physical shocks, temperature fluctuations, fatigue, and wear and tear. Further, device manufacturers want the freedom to substitute different actuators at will based on cost, availability and performance characteristics without adversely affecting the haptic feedback provided by the device or requiring costly reconfiguration by hand.